[Ori]

Quote:

Originally Posted by Johan in Brabant Yours looks vaguely similar but with an DC servo instead of output cap. Correct?

That's correct, Johan. I tried a passive filter and it's insufficient, so a discrete stage is prefered. This is still work in progress, so no schematic for now...
If you trace the Zhalou D1.2 board then you'll find that it's coming single-ended out of the DAC chip, but more surprising is the fact that the two channels use opposite phase outputs... Unless you deal with that phase inversion in circuit, you will have to solder very thin wires to very thin traces of the DAC chip, so this is not a project for the faint of heart. I opted for a differential out from the DAC chip, although my circuit outputs only single-ended at this time.
The Zhaolu D1.3 had a great sound, but it was still a notch below my reference unit. I was listening today with the discrete output circuit to a few test tracks and I noticed less distortion in a certain recording vs. my reference unit, so it looks promising. Some people complained about the bass impact of the Zhaolu. If it ever was an issue, it just became history... I feel that I'm getting a bit more 'speed' and a bigger overall soundstage, but this is only from a brief listen, so I won't come to any conclusions yet. I'll have to run more auditions after modifying a few details...
Quote:

Originally Posted by RogerWilco Nice ori--is that the unit you modded for bill?

This is indeed Bill's unit, now on its second trip to San Jose... I'm going to tell Bill that it sounds horrible so I can keep it around for a few more weeks... We'll be comparing to a modded D1.3 and a new D2.0 soon.

 

[Johan in Brabant]

Quote:

Originally Posted by Ori If you trace the Zhalou D1.2 board then you'll find that it's coming single-ended out of the DAC chip, but more surprising is the fact that the two channels use opposite phase outputs... Unless you deal with that phase inversion in circuit, you will have to solder very thin wires to very thin traces of the DAC chip, so this is not a project for the faint of heart. I opted for a differential out from the DAC chip, although my circuit outputs only single-ended at this time.

Hello Ori,

now you´ve got me confused. I´m not at home so I can´t check but on the Zhaolu board I´ve got the circuit is surprisingly similar to page 20 on this:
http://www.asahi-kasei.co.jp/akm/en/...393/ek4393.pdf

I also checked the traces and found that either phase from the dac go on either side of the pcb (so one phase on top and the other over the bottom).
It would therefor be truly balanced. It did take some time to figure this out and at first I thought it was like you observed.

So either you´ve got a different board (mine says 1.2 but parts on it are as the 1.3 configuration) or I am mistaken. Unlikely but I must admit not beyond the realm of possibility

For connecting the discrete stage I would remove the 2 resistors coming from the dac, so I would not have to deal with soldering on the dac chip itself.

Anyhow, could you point me to a starter for a dc servo to use? Once I have a basic circuit I think I will be able to figure it out.
I really do not want to spoil the sound of this very fine dac with a capacitor; or put in other words: spend a zillion hours on selecting the "right" one.

Regards and thanks,
Johan

 

[SonicDawg]

Since this seems to be the most active Zhaolu thread, I might as well ask my question here: When I plug my amp in the middle row of RCA (the headphone out), will this turn the Zhaolu into a preamp? But wouldn't then the internal amp interfere with the signal?

 

[philodox]

Quote:

Originally Posted by Ori it was still a notch below my reference unit.

What is your reference unit?

 

[Ori]

Quote:

Originally Posted by Johan in Brabant I also checked the traces and found that either phase from the dac go on either side of the pcb

Thanks for this tip! Looks like you are right...

Quote:

Originally Posted by Johan in Brabant Anyhow, could you point me to a starter for a dc servo to use? Once I have a basic circuit I think I will be able to figure it out. I really do not want to spoil the sound of this very fine dac with a capacitor; or put in other words: spend a zillion hours on selecting the "right" one.

Johan, there is just no way around that unless you complicate life with a digital servo. The capacitor would get into the low-frequency response of the loop if you feed the correction signal into an active circuit, and that includes modulating a current source.
I went for a simple implementation and summed the correction signal with the negative phase. The trick is to size the resistors in a way that the integrating capacitor is small, so you can (eventually) use a decent film cap for the task rather than having to put a large value metalized crap in there...
The last advice for a differential amp. If you want full symmetery then you either build a differential "opamp" with a lot of gain and equalize things with a lot of feedback (might as well use a standard opamp) or you go for a minimalist circuit and tweak it manualy. Either approach is a compromise but the minimalist circuit has a better sonic potential.
The best thing you'll do is to simulate the whole circuit and refine it on the computer instead of jumping in and building a feedback circuit by gut feel. My minimalist circuit is very sensitive to component values, so the simulation was mandatory. I couldn't just copy a "standard" circuit and expect it to work.

 

[Ori]

Quote:

Originally Posted by philodox What is your reference unit?

Revox B-225 with minor modifications. If you have never listened to one then you just don't know what you're missing.

 

[Jon L]

Quote:

Originally Posted by Ori Revox B-225 with minor modifications. If you have never listened to one then you just don't know what you're missing.

Man, isn't the TDA1540 DAC chip used in Revox 14-bit chips? Now we're going WAaay back

 

[Ori]

Quote:

Originally Posted by Jon L Man, isn't the TDA1540 DAC chip used in Revox 14-bit chips? Now we're going WAaay back

Studer 1983... Made for that year only, I believe. Then they came out with the pitiful B-226 "lookalike" - not even close.

I won't tell you how many reputable pieces of gear were simply outclassed by the B-225. You'll just cry...

 

[yo2tup2]

looks like a 2.0 mod thread, buthere are the mods i did to my modded zhalou 1.3 (upgraded ps, 1ppm clock, dy2000)

opamps on dac: ad823's on the sides, dy2000 middle

opamps on power supply: ad845 (made a difference in bass and soundstage...so i'm eager to try even better opa627's)

rca outs: wbt nextgen silver

digital-input: 75ohm bnc connector

hookup wiring: 24gauge silver (separated the grounds on the analog output)

ferrites around the wires from power supply to the clock and dac

removed xlr's and headphone amp

dampened the chassis with soundcoat type material

using a jelly fish type power cord

rubycon za capacitors



i found the most significant improvement came from replacing the stock pos rca outputs with high quality rca's AND the digital-in rca with a BNC. these two mods made my system sound REAL like no other mod has done, as well as giving a deep cavernous soundstage. it made everything become so smooth and natural without any signs of "digitalized" sounds. the bnc especially made the background totally black.

 

[Tachikoma]

Quote:

i found the most significant improvement came from replacing the stock pos rca outputs with high quality rca's AND the digital-in rca with a BNC. these two mods made my system sound REAL, as well as giving a deep cavernous soundstage. i everything is so smooth and natural without any signs of "digitalized" sounds.

How much did those two mods cost you?

 

[yo2tup2]

Quote:

Originally Posted by Tachikoma How much did those two mods cost you?

the bnc jack for digital in was $3.

you can get high quality rca jacks for the output from vampire or cardas for around $5 each. they should be a nice improvement over stock.

i, however, opted for the best....wbt nextgen silvers

i found them for around $35 each...and i like them a lot

 

[Johan in Brabant]

Quote:

Originally Posted by Ori Johan, there is just no way around that unless you complicate life with a digital servo..... The best thing you'll do is to simulate the whole circuit and refine it on the computer instead of jumping in and building a feedback circuit by gut feel.

Thanks for the input Ori.

Dang it: I hate trade-offs

Seems like the SACD-enhancer idea with DC servo is not the route for me.

For now I probably will start with building the standard 1 opamp AD1852 output (as per datasheet) using a discrete opamp; maybe get one with an adjustable DC offset.

Cheers,
Johan

 

[bizkid]

Did anyone try 3 DY2000? The middle DY2000 improves sound so much, why not put them everywhere?

Maybe i'll try that, im going to order eddies modded zhaolu but keep my stock one for a sidebyside comparison, so an additional DY2000 wont hurt much.

Eddie also suggested the AD797 for warm mids/thick vocals, might be a good match for my A900LTD. If it keeps the lively sound of the DY2000 ill be using that one in the middle.

 

[Gabe Logan]

How easy is it to install the digital input yo2tup2?

 

[bhiggins]

Quote:

Originally Posted by bizkid Eddie also suggested the AD797 for warm mids/thick vocals, might be a good match for my A900LTD. If it keeps the lively sound of the DY2000 ill be using that one in the middle.

I have been considering trying the AD797 in place of the LT1057 myself - I used the LT1056/57 for audio back in the early nineties and while it was a very good part then, I'm certain it has been bettered in recent years. I've got my brown dog adapters and my short list of op-amps to order is currently:

Duals - AD8620, AD8066, LM6172
Singles - AD797, OPA627

Has anyone traced the output circuit yet? I am curious if the DY2000 position is the one that drives the single-ended outputs. If so, stability and output current will probably be important parameters for this part.